Correctly load nested relationships for polymorphic relations

src/Illuminate/Database/Eloquent/Relations/MorphTo.php

@@ -5,6 +5,8 @@
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\Builder;
 use Illuminate\Database\Eloquent\Collection;
+use Illuminate\Support\Collection as BaseCollection;
+use Illuminate\Support\Str;
 
 class MorphTo extends BelongsTo
 {
@@ -176,6 +178,8 @@ protected function getResultsByType($type)
         $key = $instance->getTable().'.'.$instance->getKeyName();
 
         $query = clone $this->query;
+
+        $query->setEagerLoads($this->getEagerLoadsForInstance($instance));
         $query->setModel($instance);
 
         return $query->whereIn($key, $this->gatherKeysByType($type)->all())->get();
@@ -210,6 +214,19 @@ public function createModelByType($type)
         return new $class;
     }
 
+    protected function getEagerLoadsForInstance(Model $instance)
+    {
+        $eagers = BaseCollection::make($this->query->getEagerLoads());
+
+        $eagers = $eagers->filter(function ($constraint, $relation) {
+            return Str::startsWith($relation, $this->relation.'.');
+        });
+
+        return $eagers->keys()->map(function ($key) {
+            return Str::replaceFirst($this->relation.'.', '', $key);
+        })->combine($eagers)->merge($instance->getEagerLoads())->all();
+    }
+
     /**
      * Get the foreign key "type" name.
      *

tests/Database/DatabaseEloquentPolymorphicIntegrationTest.php

@@ -0,0 +1,231 @@
+<?php
+
+use Carbon\Carbon;
+use Illuminate\Database\Connection;
+use Illuminate\Pagination\Paginator;
+use Illuminate\Database\Query\Builder;
+use Illuminate\Database\Eloquent\SoftDeletes;
+use Illuminate\Database\Capsule\Manager as DB;
+use Illuminate\Database\Eloquent\SoftDeletingScope;
+use Illuminate\Database\Eloquent\Model as Eloquent;
+
+class DatabaseEloquentPolymorphicIntegrationTest extends PHPUnit_Framework_TestCase
+{
+    public function setUp()
+    {
+        $db = new DB;
+
+        $db->addConnection([
+            'driver'    => 'sqlite',
+            'database'  => ':memory:',
+        ]);
+
+        $db->bootEloquent();
+        $db->setAsGlobal();
+
+        $this->createSchema();
+    }
+
+    /**
+     * Setup the database schema.
+     *
+     * @return void
+     */
+    public function createSchema()
+    {
+        $this->schema()->create('users', function ($table) {
+            $table->increments('id');
+            $table->string('email')->unique();
+            $table->timestamps();
+        });
+
+        $this->schema()->create('posts', function ($table) {
+            $table->increments('id');
+            $table->integer('user_id');
+            $table->string('title');
+            $table->text('body');
+            $table->timestamps();
+        });
+
+        $this->schema()->create('comments', function ($table) {
+            $table->increments('id');
+            $table->integer('commentable_id');
+            $table->string('commentable_type');
+            $table->integer('user_id');
+            $table->text('body');
+            $table->timestamps();
+        });
+
+        $this->schema()->create('likes', function ($table) {
+            $table->increments('id');
+            $table->integer('likeable_id');
+            $table->string('likeable_type');
+            $table->timestamps();
+        });
+    }
+
+    /**
+     * Tear down the database schema.
+     *
+     * @return void
+     */
+    public function tearDown()
+    {
+        $this->schema()->drop('users');
+        $this->schema()->drop('posts');
+        $this->schema()->drop('comments');
+    }
+
+    public function testItLoadsRelationshipsAutomatically()
+    {
+        $this->createUsers();
+
+        $taylor = TestUser::first();
+        $taylor->posts()->create(['title' => 'A title', 'body' => 'A body'])
+            ->comments()->create(['body' => 'A comment body', 'user_id' => 1])
+            ->likes()->create([]);
+
+        $like = TestLikeWithSingleWith::first();
+
+        $this->assertTrue($like->relationLoaded('likeable'));
+
+        $this->assertEquals(TestComment::first(), $like->likeable);
+    }
+
+    public function testItLoadsNestedRelationshipsAutomatically()
+    {
+        $this->createUsers();
+
+        $taylor = TestUser::first();
+        $taylor->posts()->create(['title' => 'A title', 'body' => 'A body'])
+               ->comments()->create(['body' => 'A comment body', 'user_id' => 1])
+               ->likes()->create([]);
+
+        $like = TestLikeWithNestedWith::first();
+
+        $this->assertTrue($like->relationLoaded('likeable'));
+        $this->assertTrue($like->likeable->relationLoaded('owner'));
+
+        $this->assertEquals($taylor, $like->likeable->owner);
+    }
+
+    /**
+     * Helpers...
+     */
+    protected function createUsers()
+    {
+        TestUser::create(['id' => 1, 'email' => 'taylorotwell@gmail.com']);
+    }
+
+    /**
+     * Get a database connection instance.
+     *
+     * @return Connection
+     */
+    protected function connection()
+    {
+        return Eloquent::getConnectionResolver()->connection();
+    }
+
+    /**
+     * Get a schema builder instance.
+     *
+     * @return Schema\Builder
+     */
+    protected function schema()
+    {
+        return $this->connection()->getSchemaBuilder();
+    }
+}
+
+/**
+ * Eloquent Models...
+ */
+class TestUser extends Eloquent
+{
+    protected $table = 'users';
+    protected $guarded = [];
+
+    public function posts()
+    {
+        return $this->hasMany(TestPost::class, 'user_id');
+    }
+}
+
+/**
+ * Eloquent Models...
+ */
+class TestPost extends Eloquent
+{
+    protected $table = 'posts';
+    protected $guarded = [];
+
+    public function comments()
+    {
+        return $this->morphMany(TestComment::class, 'commentable');
+    }
+
+    public function owner()
+    {
+        return $this->belongsTo(TestUser::class, 'user_id');
+    }
+}
+
+/**
+ * Eloquent Models...
+ */
+class TestComment extends Eloquent
+{
+    protected $table = 'comments';
+    protected $guarded = [];
+
+    public function owner()
+    {
+        return $this->belongsTo(TestUser::class, 'user_id');
+    }
+
+    public function commentable()
+    {
+        return $this->morphTo();
+    }
+
+    public function likes()
+    {
+        return $this->morphMany(TestLike::class, 'likeable');
+    }
+}
+
+class TestLike extends Eloquent
+{
+    protected $table = 'likes';
+    protected $guarded = [];
+
+    public function likeable()
+    {
+        return $this->morphTo();
+    }
+}
+
+class TestLikeWithSingleWith extends Eloquent
+{
+    protected $table = 'likes';
+    protected $guarded = [];
+    protected $with = ['likeable'];
+
+    public function likeable()
+    {
+        return $this->morphTo();
+    }
+}
+
+class TestLikeWithNestedWith extends Eloquent
+{
+    protected $table = 'likes';
+    protected $guarded = [];
+    protected $with = ['likeable.owner'];
+
+    public function likeable()
+    {
+        return $this->morphTo();
+    }
+}